The present invention generally relates to the field of rotational position sensors, and more specifically to a magnetic rotational position sensor for sensing each rotational position of a control shaft about an axis over a definable range of rotation.
Electronic fuel injected engines used in motor vehicles typically embody a microprocessor based control system. Fuel is metered or injector activation time is varied in accordance with various engine parameters including the regulation of air flow into the engine via a rotational position of a throttle diaphragm relative to a closed position of the throttle diaphragm. Typically, a shaft is adjoined to the throttle diaphragm to synchronously rotate the throttle diaphragm as the shaft is rotated between the closed position and a maximal open position of the throttle diaphragm. Rotational position sensors are adjoined to the shaft to sense each rotational position of the shaft, i.e. each degree of rotation of the shaft relative to the closed position, whereby the rotational position of the throttle diaphragm relative to the closed position is sensed.
One of the problems associated with the prior magnetic rotational position sensors is magnetic hysteresis. Magnetic hysteresis causes an offset error signal to be provided whenever a magnetic element of the sensor, e.g. a magnetic pole piece or a magnetic rotor, is advanced from and returned to a reference position of the magnetic element. Annealing the magnetic element can minimize, but never eliminate, magnetic hysteresis. What is therefore needed is a novel and unique magnetic rotational position sensor that does not experience magnetic hysteresis.
The present invention is a magnetic rotational position sensor that overcomes the aforementioned drawback associated with prior magnetic rotational position sensors. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention described in detail herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the present invention disclosed herein can be described briefly.
In accordance with a first form of the present invention, the magnetic rotational position sensor comprises a ring pole piece defining an air gap area and a magnet disposed within the air gap area to thereby generate a magnetic field therein. The ring pole piece includes a first pole segment, a second pole segment, and a third pole segment. The first pole segment is adjoined to the second pole segment and the third pole segment. The second pole segment and the third pole segment are spaced from each other. The magnet has a first pole surface and a second pole surface. The first pole surface is facing and spaced from the first pole segment. The second pole surface is facing the second pole segment and the third pole segment.
Further forms, objects, features, aspects, benefits, advantages, and embodiments of the present invention shall become apparent from the detailed description and drawings provided herewith.